1. Field of the Invention
This invention relates to improvements in a seat reclining system for a vehicle, and more particularly to a structure for reinforcing a base plate of the seat reclining system.
2. Description of the Prior Art
Modern automotive vehicles are equipped with a seat reclining system which adjusts the rotational position of a seat back of a vehicle seat forward or rearward in order that a vehicle occupant seated on the seat can ensure his optimum and comfortable posture. In a recent tendency in which weight-lightening of vehicular parts is being promoted to meet the requirement of weight-lightening of the vehicle, weight-lightening is required also for the seat reclining systems. In view of this, the thickness of a base plate of the seat reclining system is reduced as compared with a conventional one thereby accomplishing lightening of the seat reclining system.
More specifically, right-side and left-side base plates made of metal are fixed through suitable fixing members to a vehicle floor or fixed respectively to right-side and left-side seat slide devices fixed on the vehicle floor. A seat cushion of the vehicle seat is disposed between the base plates. Each base plate is disposed vertical to the vehicle floor. An arm plate is hingedly connected through a locking mechanism to each base plate. The seat back of the vehicle seat is installed to the arm plate. The locking mechanism is a control section for adjusting the inclination angle of the seat back. Accordingly, the base plate must have a sufficient strength to sustain a load applied to the seat back, so that the thickness of the material (metal plate) of the base plate has been conventionally increased thereby unavoidably increasing the weight of the seat reclining system.
There is one locking system for the seat reclining system, in which two locking mechanisms are respectively installed to the right-side and left-side base plates. Another locking system is arranged such that only one locking mechanism is installed to one of the right-side and left-side base plates so that the other base plate is formed as a freely movable hinge. Concerning the structure of the locking mechanism, hitherto one in which lock parts are assembled to the base plate is in the mainstream; however, recently one in which a unitized locking mechanism is assembled between the base plate and the arm plate has been used. In connection with the latter one, the arm plate is formed to have a reduced thickness and has a flange section along the periphery of the arm plate.